Startle modulation before, during and after exposure to emotional stimuli.

Although affective modulation of the startle reflex is a highly replicable effect, the majority of studies have administered startle probes during exposure to affective stimuli. To examine more comprehensively the temporal course of startle potentiation, we assessed blink modulation before, during and immediately after exposure to positive, negative and neutral pictures. During each trial, cues about the affective content of pictures were presented, after which acoustic startle probes were delivered either before picture onset, during picture onset or immediately after picture offset. As expected, we observed a linear relation between picture valence and startle amplitude during picture viewing. Surprisingly, startle amplitude was larger while anticipating pleasant and unpleasant pictures relative to neutral pictures. No significant effects were observed during the offset phase. These results indicate that startle modulation is conditional upon temporal factors linked to stimulus onset and offset.     

Nociception and baroreceptor stimulation in hypertension-prone men and women

We examined the effects of baroreceptor stimulation on nociceptive responding in men and women with a positive or negative parental history of hypertension. The effects of three baroreceptor conditions (stimulation, inhibition, and control) on subjective pain and nociceptive responding were evaluated during electrocutaneous sural nerve stimulation. Pain ratings were lower in men with positive parental history relative to men with negative parental history, but this difference was not found in women. Both stimulatory and inhibitory baroreceptor conditions were associated with reduced pain reports compared to the control condition. There were no significant differences in nociceptive responding as a function of parental history of hypertension. Although this study confirms a link between hypoalgesia and risk for hypertension in men, it does not support the hypothesis that this attenuated pain perception is due to enhanced baroreceptor activity.     

Temporal course of emotional startle modulation in schizophrenia patients.

The temporal course of startle reflex modulation to emotional pictures was investigated in 49 relatively asymptomatic schizophrenia outpatients and 46 normal controls. Participants viewed pleasant, neutral and unpleasant pictures, which were presented for 6 s and acoustic startle probes were delivered at five different times after picture onset. Replicating previous findings schizophrenia patients showed the same affective modulation of the startle reflex as healthy controls when probes were presented later during the picture-viewing period (3800 ms). For the early probe times (300 and 800 ms), affective pictures proved to be the effective prepulse stimuli resulting in a clear Prepulse inhibition (PPI) effect in both groups. In contrast to previous findings, the PPI of startle response was not stronger during processing emotional stimuli relative to neutral stimuli. For control subjects, blink reflexes were larger for unpleasant pictures compared with neutral and pleasant pictures, representing an early activation of motivational systems. Schizophrenia patients on the other hand, did not show this early affective modulation of the acoustic startle reflex.     

Affective startle modulation in anticipation and perception

Startle modulation was investigated as participants first anticipated and then viewed affective pictures in order to determine whether affective modulation of the startle reflex is similar in these different task contexts. During a 6-s anticipation period, a neutral light cue signaled whether the upcoming picture would portray snakes, erotica, or household objects; at the end of the anticipatory period, a picture in the signaled category was viewed for 6 s. Male participants highly fearful of snakes were recruited to maximize emotional arousal during anticipation and perception. Results indicated that the startle reflex was potentiated when anticipating either unpleasant (phobic) or pleasant (erotic) pictures, compared to neutral stimuli, whereas during perception, reflexes were potentiated when viewing unpleasant stimuli, and reduced when viewing pleasant pictures. The startle reflex is modulated by hedonic valence in picture perception, and by emotional arousal in a task context involving picture anticipation.     

Loss of emotional experience after traumatic brain injury: findings with the startle probe procedure

The authors used affective modulation of the eyeblink startle response to examine the impact of traumatic brain injury (TBI) on emotional reactions to pictures. Participants were 13 individuals with severe TBI and 24 controls. Participants were presented with pictures that differed in affective valence (e.g., mutilated bodies, erotic couples, and household objects) while the eyeblink startle response to an acoustic probe was measured. Startle amplitude was used to assess valence of emotional response, and startle latency was used to index interest in the pictures. Subjective ratings of the affect and arousal elicited by the various pictures were also obtained. TBI impaired startle potentiation to unpleasant pictures but not startle attenuation to pleasant pictures. Further, subjective ratings indicated that TBI participants found unpleasant pictures less arousing than did controls. The results are consistent with recent evidence of differential impairment in negative versus positive emotions after TBI and are discussed in relation to 2 competing explanations of startle modulation.     

Affective modulation of tactile startle

Two studies were conducted to investigate affective modulation of startle responses to unilateral tactile probes and to determine whether such modulation is lateralized. Right-handed undergraduates received airpuffs to the left or right temple while viewing pleasant, neutral, and unpleasant pictures. Side of probe presentation was varied between the two trial blocks of the experiment in Study 1 (n= 48) but varied randomly within trial blocks in Study 2 (n= 48). Primary results were consistent across studies. Replicating and extending the findings for acoustic probes, eyeblink responses to tactile probes were larger during unpleasant than during pleasant pictures. However, affective modulation of startle did not differ reliably between the two sides of probe presentation (sensory laterality) or the two sides of the response (motor lateralily) in either study or in a combined analysis.     

Relationships between startle and cardiovascular reactivity

Although startle and cardiovascular reactivity have been studied extensively, little is known about their relationship. In the present study, we examined cardiovascular responses and affective startle modulation in 112 normotensive individuals varying in self-reported fearfulness and parental cardiovascular health history. An initial intense noise burst elicited a phasic cardiac acceleration that was larger for fearful individuals. Startle blink responses were larger during aversive than during pleasant relaxing imagery but did not differ with fear group. Cognitive challenge tasks elicited heart rate and blood pressure increases that were unrelated to fearfulness or parental health history. However, greater startle potentiation by aversive imagery predicted larger pressor responses to cognitive challenge, especially among men. The observed relationship between startle and cardiovascular reactivity suggests a common mechanism for their affective modulation.     

State anxiety and affective physiology: effects of sustained exposure to affective pictures

Effects of sustained exposure to emotional stimuli on affective reactions and their recovery were examined to determine whether increasing exposure to a specific emotional content (e.g., unpleasant) cumulatively affects physiological responses; and whether motivational activation persists following sustained exposure. Participants viewed pleasant, neutral, and unpleasant IAPS pictures, presented in blocks separated by an inter-block interval. With increasing exposure to unpleasant pictures, startle magnitude showed greater potentiation, and corrugator EMG activity increased. Both affective startle and corrugator modulation persisted following exposure to unpleasant pictures. The cumulative effects of sustained exposure to unpleasant pictures were enhanced for those reporting higher state anxiety, consistent with the hypothesis that sustained aversive exposure leads to increased defensive activation. These findings suggest sustained exposure to unpleasant pictures may induce a short-term mood state, and may be a useful paradigm to study individuals who vary in symptoms of anxiety.     

Temporal stability of the emotion-modulated startle response

In the present study, we examined the stability of one measure of emotion, the emotion-modulated acoustic startle response, in an undergraduate sample. Using the acoustic startle paradigm on two different occasions, we measured stability of affective modulation of the startle response during and following the presentation of pictures selected to be of positive, negative, or neutral emotional valence. The two assessments were separated by 4 weeks. Two groups of subjects were compared: one group that viewed the same pictures at each assessment and a second group that viewed different pictures at the second assessment. We found that viewing different pictures at two assessments separated by 4 weeks yielded moderate stability of the emotion modulation of startle magnitude, whereas subjects who viewed the same pictures at both assessments showed poor stability. Furthermore, this difference was due to the stability of responses to high versus low arousal pictures, not to differences in valence.     

Addressing the specificity of affective startle modulation: fear versus disgust.

Previous research is equivocal regarding whether startle reflex eyeblink is specifically sensitive to the emotion of fear, or is more generally influenced by the valence dimension of emotion. Thirty-five undergraduate participants (17 male) viewed 60 pictures from five affective categories (pleasant, neutral, fear, disgust-blood, and disgust-other). Bilateral eyeblink EMG responses to acoustic startle probes were assessed during 2/3 of picture presentations, and 1/3 of intertrial intervals. Left corrugator and levator EMG responses to no-startle pictures were also examined. Supporting an emotional valence model of affective startle modulation, the startle potentiation effect was not specific to fear materials. In fact, women, but not men, had larger startles during disgust compared with fear pictures. Both corrugator and levator EMG responses were greater to disgust than fear stimuli. These findings limit the generalizability of corrugator as an index of all negative emotions and extend evidence for the specificity of levator to disgust.     

Affective modulation of eyeblink reactions to noxious sural nerve stimulation: a supraspinal measure of nociceptive reactivity?

Research suggests affective picture-viewing modulates subjective and physiological reactions to noxious stimulation (pain report, heart rate acceleration, skin conductance response, nociceptive flexion reflex). Because the nociceptive flexion reflex (a spinal reflex) is modulated by picture-viewing, this suggests affective processes are able to modulate afferent nociception at spinal levels. This highlights the importance of assessing nociceptive reactivity from physiological measures mediated at different levels of the neuraxis (spinal vs. supraspinal) to help elucidate the mechanisms associated with pain regulation. The present study examined whether affective pictures modulate eyeblink reactions (a supraspinal reflex) to noxious stimulation. Healthy men and women (N=23) were recruited from the psychology subject pool to participate. Pictures (attack, loss, neutral, food, erotica) that manipulated affective valence and arousal were presented and noxious electrodermal stimulations were delivered to the sural nerve. Picture duration (500-ms vs. 6-s) was also manipulated, balanced across picture content. Results suggested affective valence and arousal contributed to the modulation of eyeblinks. Eyeblinks were larger during highly arousing unpleasant pictures (attack) than highly arousing pleasant pictures (erotica), but low arousal pictures (loss, food) did not lead to significant modulation. Affective modulation was independent of picture duration or the perceived painfulness of noxious stimulation. This study suggests eyeblink reactions can serve as a supraspinal outcome in procedures used to study affective modulation of pain and nociception.     

Early- and late-onset startle modulation in unipolar depression

In two experimental sessions, we assessed early- and late-onset acoustic startle eyeblink modulation and subjective ratings of emotional pictures by nondepressed participants and by unipolar depressed participants. Depressed participants were assessed before and after treatment with the antidepressant medication Bupropion SR. Both depressed and nondepressed participants exhibited arousal-dependent startle modulation to early probes occurring 300 ms after picture onset. Nondepressed participants demonstrated the expected valence-dependent startle modulation to late probes (3,500-4,500 ms post-onset). In contrast, the late-probe blink magnitudes of depressed patients were unrelated to picture valence. This pattern of group differences was not moderated by treatment. There were no between-group differences in self-report ratings to pictures. These results suggest that depression may be characterized by anomalous responses to affective stimuli and that startle modulation can be a more sensitive index of affective response deficits linked to depression than self-report measures.     

Probing affective pictures: Attended startle and tone probes

Reflexive eyeblinks to a startle probe vary with the pleasantness of affective pictures, whereas the corresponding P300 varies with emotional arousal. The impact of attention to the probe on these effects was examined by varying task and probe type. Probes were either nonstartling tones or startling noises presented during affective picture viewing. Half the participants performed a task requiring attention to the probes; the other participants were told to ignore the probes. Blinks to the startle probe varied with picture pleasantness for both task and nontask conditions. In contrast, P300 magnitudes for both startle and tone probes were reduced during emotionally arousing pictures, irrespective of pleasantness, in task and nontask conditions. Further, attending to the startle probe prompted an augmentation of N100 during unpleasant pictures. The data suggest that affective modulation of probe responses reflects obligatory processes in picture perception.     

Startle modulation by affective faces

Startle reflex modulation by affective pictures is a well-established effect in human emotion research. However, much less is known about startle modulation by affective faces, despite the growing evidence that facial expressions robustly activate emotion-related brain circuits. In this study, acoustic startle probes were administered to 37 young adult participants (20 women) during the viewing of slides from the Pictures of Facial Affect set including neutral, happy, angry, and fearful faces. The effect of expression valence (happy, neutral, and negative) on startle magnitude was highly significant (p < .001). Startle reflex was strongly potentiated by negative expressions (fearful and angry), however, no attenuation by happy faces was observed. A significant valence by gender interaction suggests stronger startle potentiation effects in females. These results demonstrate that affective facial expressions can produce significant modulation of the startle reflex.     

Affect, attention, or anticipatory arousal? Human blink startle modulation in forward and backward affective conditioning

Affect modulates the blink startle reflex in the picture-viewing paradigm, however, the process responsible for reflex modulation during conditional stimuli (CSs) that have acquired valence through affective conditioning remains unclear. In Experiment 1, neutral shapes (CSs) and valenced or neutral pictures (USs) were paired in a forward (CS-->US) manner. Pleasantness ratings supported affective learning of positive and negative valence. Post-acquisition, blink reflexes were larger during the pleasant and unpleasant CSs than during the neutral CS. Rather than affect, attention or anticipatory arousal were suggested as sources of startle modulation. Experiment 2 confirmed that affective learning in the picture-picture paradigm was not affected by whether the CS preceded the US. Pleasantness ratings and affective priming revealed similar extents of affective learning following forward, backward or simultaneous pairings of CSs and USs. Experiment 3 utilized a backward conditioning procedure (US-->CS) to minimize effects of US anticipation. Again, blink reflexes were larger during CSs paired with valenced USs regardless of US valence implicating attention rather than anticipatory arousal or affect as the process modulating startle in this paradigm.     

Affective modulation of eyeblink reactions to noxious sural nerve stimulation: A supraspinal measure of nociceptive reactivity?

Research suggests affective picture-viewing modulates subjective and physiological reactions to noxious stimulation (pain report, heart rate acceleration, skin conductance response, nociceptive flexion reflex). Because the nociceptive flexion reflex (a spinal reflex) is modulated by picture-viewing, this suggests affective processes are able to modulate afferent nociception at spinal levels. This highlights the importance of assessing nociceptive reactivity from physiological measures mediated at different levels of the neuraxis (spinal vs. supraspinal) to help elucidate the mechanisms associated with pain regulation. The present study examined whether affective pictures modulate eyeblink reactions (a supraspinal reflex) to noxious stimulation. Healthy men and women (N = 23) were recruited from the psychology subject pool to participate. Pictures (attack, loss, neutral, food, erotica) that manipulated affective valence and arousal were presented and noxious electrodermal stimulations were delivered to the sural nerve. Picture duration (500-ms vs. 6-s) was also manipulated, balanced across picture content. Results suggested affective valence and arousal contributed to the modulation of eyeblinks. Eyeblinks were larger during highly arousing unpleasant pictures (attack) than highly arousing pleasant pictures (erotica), but low arousal pictures (loss, food) did not lead to significant modulation. Affective modulation was independent of picture duration or the perceived painfulness of noxious stimulation. This study suggests eyeblink reactions can serve as a supraspinal outcome in procedures used to study affective modulation of pain and nociception.     

Simple reaction time as a function of the phase of the cardiac cycle in young adults at risk for hypertension

Modulation of simple reaction time over the cardiac cycle, which is likely to be mediated by activation of arterial baroreceptors, may be moderated by individual difference factors that affect baroreceptor activation, such as risk for hypertension. This study examined arterial baroreceptor effects on simple reaction times by presenting vibrotactile stimuli at six intervals after the R-wave of the electrocardiogram (0, 150, 300, 450, 600, and 750 ms) in 113 young men and women whose resting blood pressure and parental history of hypertension were ascertained. Reaction times were slower early in the cardiac cycle compared to later. However, these cycle time effects were not moderated by sex, resting blood pressure, or parental history of hypertension. In conclusion, cardiac-related cortical interference was not moderated by risk for hypertension.     

Independence of valence modulation and prepulse inhibition of startle

This study sought to determine whether prepulse inhibition and valence modulation of startle are independent, both within and across individuals. Acoustic probes (105 dB) were delivered as 68 undergraduate s viewed pleasant, neutral, and unpleasant pictures. Weak acoustic stimuli (8 dB above background) preceded half of the probes by 120 ms. As expected, startles were larger during unpleasant than during pleasant pictures, and smaller on prepulse than no-prepulse trials. In general, valence modulation and prepulse inhibition of startle were unrelated. That is, prepulse inhibition was consistent across affective states, valence modulation did not differ between no-prepulse and prepulse trials, and valence modulation and prepulse inhibition effects were uncorrelated across individuals. Analysis of raw and percent modification scores generally led to similar conclusions. It is concluded that valence modulation and prepulse inhibition are independent startle modulatory phenomena, although this conclusion is tempered by a finding of poor internal consistency reliability for valence modulation.     

Modulation of spinal reflexes: Arousal, pleasure, action

The human startle reflex is reliably modulated by the affective valence of foreground pictures, with larger reflexes elicited when viewing unpleasant relative to pleasant scenes. If this modulation is due to priming of the defensive startle reflex by an aversive foreground, a different pattern should occur for a reflex that is not inherently defensive in nature. In the current study, affective modulation was investigated using the spinal tendinous (T) reflex, which is well documented as sensitive to differences in arousal and is involved in actions that are both appetitively and defensively motivated. As such, T reflexes elicited during unpleasant pictures were not expected to be augmented relative to those elicited in the context of pleasant pictures. Results showed that T reflexes were facilitated during processing of arousing stimuli – either pleasant or unpleasant relative to low-arousal neutral materials. These effects of emotional stimuli on T-reflex amplitude are consistent with the hypothesis that motivational priming underlies affective reflex modulation.     

The influence of attachment representation on parental perception and interpretation of infant emotions: A multilevel approach

The aim of the study was to investigate parental perception and interpretation of infant emotional expression depending on their attachment representation. Forty‐six parents' responses to infant pictures depicting positive, neutral, and negative emotions were assessed on the level of affective judgments (valence, arousal), mimic responses (facial muscle activity), and of the eyelid reflex (using the startle paradigm). Results revealed small differences between parents of different attachment representations with respect to their subjective evaluations. However, secure parents, as compared to insecure ones, showed a positive bias in their mimic responses to infant pictures. The modulation of the startle response indicated a negative evaluation of negative infant emotion expressions in dismissing parents, while an augmentation of the startle response to negative infant emotions could not be observed in secure and preoccupied parents. The findings highlight the role of attachment experiences for emotional information processing in parents and its consequences for parental behavior. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52: 411–423, 2010.